1. Field of the Invention
The present invention generally relates to methods and compositions which promote the controlled and programmable growth and strengthening of bone.
2. Description of Related Art
Various bone diseases, injuries, or surgical interventions in humans and other vertebrates result in bone defects or fractures. Bone growth or restitution is often desired to alleviate these conditions. The bone growth may be desired in areas where bone previously existed and is partially or completely absent, or where its continuity has been disrupted. Situations where such regeneration of bone is necessary or desirable include the healing of fractures, or increasing the bone mass in osteoporotic bones. Bone growth may also be desired in areas where bone did not previously exist. Such bone generation is desirable, e.g., for filling defects, such as caused by removal of tumors or intervertebral discs, for correcting congenital deformities such as cleft palates, or for forming a strong connection between a prosthesis such as a joint replacement and an adjacent bone.
Various compositions are known which are designed to encourage bone growth. These compositions are generally applied to bone defects or fractures to provide an osteoinductive and osteoconductive environment. Examples include those disclosed in U.S. Pat. Nos. 5,563,124; 4,642,120; 5,755,792; 5,830,493; and 5,711,957; PCT Patent Publications WO 94/15653; WO 95/13767; WO 98/56433; and WO 97/32591; and European Patent EP 754,466. Additionally, such compositions are available commercially, including demineralized bone matrix compositions such as Grafton(copyright) (Osteotech, Eatontown, N.J.). These compositions generally comprise a porous solid, semisolid, paste or gel material including materials such as gelatin, hyaluronic acid, collagen, amylopectin, demineralized bone matrix, and/or calcium carbonate, to create an osteoconductive environment. The compositions also often include osteoinductive growth factors such as transforming growth factor-xcex2, bone morphogenic protein, or basic fibroblast gorwth factor. It may be noted that combinations of chitosan with demineralized bone matrix and/or ground or chipped cancellous bone are unknown. Methods for filling bone defects utilizing compositions constituted solely of chitin or chitosan are also unknown.
In spite of the availability of numerous compositions to encourage bone growth, problems still occur in attempts to achieve satisfactory growth of bone to fill bone defects, connect prostheses to existing bone, and fuse fractures and bone grafts to existing bone. Therefore, there is an ongoing need for new compositions to provide alternatives to existing compositions for encouraging bone growth.
Among the several objects of the present invention may be noted the provision of compositions which promote bone formation and growth. A more specific object of the invention is the provision of compositions which stimulate bone formation and growth through the stimulation of angiogenesis and osteogenesis. Another object of the invention is the provision of methods for stimulating bone formation and growth through the use of angiogenesis-stimulating compositions.
Briefly, therefore, the present invention is directed to a composition comprising the following components: (a) one or more materials selected from the group consisting of fibroblast growth factors, vascular endothelial growth factors, endothelial cell growth factors, transforming growth factors, chitosan, bone, platelet derived endothelial growth factors, placental growth factors, angiogenin, interleukin-8, granulocyte colony-stimulating growth factor, and supernatant fluid from a culture of cells known to produce angiogenic factors; (b) a material comprising demineralized bone matrix, non-decalcified bone matrix, with or without hyaluronic acid; (c) a scaffolding material selected from the group consisting of cancellous bone, chitosan, chitosan-protein, and chitin-protein fibers; and (d) a gel material selected from the group consisting of chitosan, imidazolyl chitosan, methylpyrrolidinone chitosan, carbodiimide chitosan, glutaraldehyde chitosan, alginate, a mixture of alginate with chitosan or a chitosan derivative, hyaluronic acid, and a mixture of hyaluronic acid with chitosan or a chitosan derivative.
Additionally, the present invention is directed to a composition comprising the following components: (a) one or more angiogenesis-stimulating materials; (b) an osteoinductive material; (c) a scaffolding material; and (d) a gel material.
Moreover, the present invention is directed to a composition comprising the following components: (a) one or more angiogenesis-stimulating materials selected from the group consisting of fibroblast growth factors, vascular endothelial growth factors, endothelial cell growth factors, transforming growth factors, chitosan, bone, platelet derived endothelial growth factors, placental growth factors, angiogenin, interleukin-8, granulocyte colony-stimulating growth factor, and supernatant from cells known to produce angiogenic factors; (b) an osteoinductive material comprising demineralized bone matrix, non-decalcified bone matrix, with or without hyaluronic acid; (c) a scaffolding material selected from the group consisting of cancellous bone, chitosan, chitosan-protein, and chitin-protein fibers; and (d) a gel material selected from the group consisting of chitosan, imidazolyl chitosan, methylpyrrolidinone chitosan, carbodiimide chitosan, glutaraldehyde chitosan, alginate, and a mixture of alginate with chitosan or a chitosan derivative.
Furthermore, the present invention is directed to a composition for promoting the growth and strengthening of bone comprising a mixture of chitosan or chitosan derivative, cancellous bone, and demineralized bone matrix. The present invention is also directed to a composition for promoting growth and strengthening of bone comprising a mixture of alginate, calcium, cancellous bone, and demineralized bone matrix. Also, the present invention is directed to a composition for promoting growth and strengthening of bone comprising a mixture of chitosan or chitosan derivative, alginate, cancellous bone, and demineralized bone matrix. Additionally, the present invention is directed to a composition for promoting growth and strengthening of bone comprising a mixture of hyaluronic acid, cancellous bone, and demineralized bone matrix.
The present invention is also directed to a method of inducing bone formation in a vertebrate. The method comprises applying the compositions described above to a site in the vertebrate where bone formation is desired.
In an additional embodiment, the present invention is directed to a method of filling a bone defect. The method comprises filling the bone defect with a rigid material consisting essentially of chitin or chitosan.